The present invention relates to a false twister, especially for producing spiral filaments, comprising a rotatably powered twister including at least one guide pulley around which the filaments are wrapped. The invention relates furthermore to a method of producing spiral filaments, more particularly in making use of a generic false twister in which at least two filaments are combined and plastically deformed in a false twister, including at least one guide pulley wrapped by the filaments.
The term filament in this case is not to be interpreted restrictive, but as also including both single and multiple filaments.
A false twister and a generic production method are known from WO 97/12091 and WO 97/12092 originated by the same Applicant. The basic configuration and function of a false twister are likewise evident from JP-A 02-269885. A false twister comprises a rotatably powered twister including at least one guide pulley. For producing spiral filaments, several filaments are combined by a suitable means, passed through the twister parallel to the axis of rotation and wrapped around the guide pulley of the twister. A downstream outfeeder serves to move the filaments through the twister, rotation of which results in plastic deformation of the filaments. This plastic deformation is already produced in the false twister. The outfeeder provided downstream of the false twister results in the already plastically deformed filaments being exposed to high forces, as a result of which the plastic deformation is detremented and undesirable stresses are introduced in the filaments.
The objective of the present invention is thus to substantially reduce the forces acting on the filaments after plastic deformation.
In accordance with the invention this objective is achieved in a false twister of the aforementioned kind in that at least one guide pulley may be powered. In the production method in accordance with the invention the force needed to move the filaments through the false twister is applied to the filaments at least in part in the false twister.
The filaments are wrapped around the guide pulley so that forces can be communicated to the filaments when the guide pulley is powered. Before entering the false twister, up until being wrapped around the guide pulley, the filaments are intertwined in thus each supporting the other. It is in this zone that in addition very high stresses are needed in the filaments to produce the desired plastic deformation. In the zone between the guide pulley and the discharge from the false twister the spirally deformed filaments are separate from each other. The forces acting on the individual filaments are small since the force needed to move the filaments is furnished by the guide pulley wrapped by the filaments. Depending on the particular application it is possible to totally eliminate an outfeeder in thus reducing the space requirement and the costs of investment.
Advantageous aspects and further embodiments of the invention read from the dependent sub-claims.
Advantageously, the guide pulley is powered by the rotation of the twister in thus enabling a separate drive for the guide pulley to be eliminated in minimizing the mass of the twister and the investment costs.
In accordance with an advantageous further embodiment, the rotary speed of the powered guide pulley and the rotary speed of the twister can be varied relative to each other to permit optimum adaptation to the marginal conditions in each case in specifically setting the spiral shape of the filaments to be produced.
In one advantageous aspect a gear unit is provided applied to the twister for powering the guide pulley, this gear unit permitting coupling the guide pulley to a separate drive element in enhancing system flexibility.
In accordance with another advantageous further embodiment, the gear unit mates with a gearwheel separate from the twister to make for a simple, rugged, cost-effective design for a long useful life.
Advantageously, the gearwheel is arranged upstream or downstream of the twister to permit optimally adapting the false twister in accordance with the invention to the various marginal conditions such as how the twister is mounted or the space available.
In a first advantageous aspect the gearwheel is arranged fixed, the rotation of the guide pulley and the rotation of the twister being automatically coupled on rotation of the twister. More particularly, the rotary speed ratio is always the same as dictated by the translation of the gear unit and gearwheel. Any change in the rotary speed of the twister is automatically communicated to the guide pulley in thus enabling complicated control and adjustment procedures to be eliminated. Fluctuations in the rotary speed of the twister are automatically compensated.
In accordance with another advantageous further embodiment, the gearwheel is secured to a perforated disk for combining the filaments in thus eliminating the need for a separate mount for the gearwheel to further reduce the costs of investment.
In a second advantageous aspect the gearwheel can be rotatively powered. When the drive for the gearwheel is halted the coupling between the rotary speed of the twister and the rotary speed of the guide pulley, as described above, is automatically instigated. In addition, the rotary speed of the guide pulley can be set independently of the rotary speed of the twister by powering the gearwheel. This permits varying the shape in forming the spiral filaments in substantially enhancing the flexibility of the false twister in accordance with the invention.
Advantageously, the gear unit comprises a shaft rotatably mounted in the twister. This shaft permits the elimination of large dimensioned gearwheels having correspondingly high moments of mass inertia.
In accordance with yet another further embodiment, the shaft is arranged substantially parallel to the axis of rotation of the twister to thus reduce the space requirement in the radial direction.
In another advantageous aspect the guide pulley is provided with radially protruding flanges for guiding the filaments, as a result of which, the filaments are prevented from slipping off of the guide pulley.
Advantageously, the guide pulley is configured conically in the portion between the flanges. This conical configuration of the guide pulley ensures that the incoming filaments are always urged to the same flange in thus reliably preventing tangling of the filaments in the region of the guide pulley.
The method in accordance with the invention provides for the force needed to move the filaments through the false twister being provided at least in part in the false twister to the filaments to substantially reduce the force acting on the already plastically deformed filaments.
Advantageously, the force needed to move the filaments is provided in the false twister (10) to the filaments in the range of 10 to 100 percent, more particularly to more than 50 percent, more than 70 percent, more than 85 percent or more than 97 percent, the precise percentage of the force provided in the false twister to the filaments depending on the individual application, more particularly on the type of filaments involved, the diameter of the filaments, the material used as well as the spiral shape desired. The method in accordance with the invention permits optimum adaptation to the various conditions in each case.
In one advantageous aspect the wrap angle of the filaments around the guide pulley, especially the wrap number, is set as a function of the force provided in the false twister. The force communicated as a maximum by the guide pulley to the filaments is an exponential function of the wrap angle. Suitable adapting the wrap angle, especially via the wrap number, prevents any unwanted slip of the filaments relative to the guide pulley.
In accordance with one advantageous further embodiment, the rotary speed of the guide pulley and the rotary speed of the twister are varied relative to each other in changing the spiral shape of the filaments, the time needed to produce a winding being computed from the rotary speed of the twister. The rotary speed of the guide pulley together with its diameter gives the rotary speed with which the filaments are moved through the twister, and thus from the time needed to produce a winding the pitch of the spirals can be computed from the rotary speed and diameter of the guide pulley. By suitably varying the rotary speed of the guide pulley and/or the rotary speed of the twister, filaments differing in pitch can thus be produced.
In accordance with one advantageous aspect the spiral filaments are directly reeled on leaving the false twister to thus eliminate the need for a downstream outfeeder in furthermore saving space and costs of investment.